Decibeloscope



NW. TL, R949 R. w. STANMYRE 2,486,890

DECIBELOSCOPE Filed May 25, 1946 2 Sheets-Sheet 1 INVENTOR. UDOLPH-WTANMY E F a s: 1 R 5 PHTORNEYS Nov. 1, 1949 R. w. STANMYRE DECIBELOSCOPE2 Sheets-Sheet 2 Filed May 25, 1946 INVENTOR.

RUDOLPH-W STANMYRE /QoMQ/ZZW/ ATTORNEYS Patented Nov. 1, 1949 UNITEDSTATES PATENT OFFICE Application May 25, 1946, Serial No. 672,222 1Claim. (Cl. 117411) This invention has to do with a device for visuallyindicating the volume or intensity, of sound, and which I refer to as adeclbeloscope.

The invention, has as an object, a device which is operable to give aclear visual indication of the volume of sounds, and which embodies astructure which is economical to manufacture and which is particularlysimple and convenient to operate.

The device has many uses such, for example,

as continuously indicating to a student of elocutlon, or a speaker, thevolume, or intensity, of his voice. In this respect, it is particularlyhelpin] to deaf persons who have extremely great difficulty in properlycontrolling the volume of their speech.

The invention consists in the novelfeatures and in the combinations andconstructions hereinafter set forth and claimed.

In describing this invention, reference is made to the accompanyingdrawings in which likecharacters designate corresponding parts in allthe views.

Figure l is a front, elevational view of a device embodying myinvention.

Figure 2 is a schematic wiring diagram illustrating the arrangement andconnection of the various elements of the device.

The device consists generally of a series of incandescent lamps, amicrophone into which the sound waves are directed, and means connectedin circuit with the microphone, and operable to energize theincandescent lamps progressively from one end of the series toward theopposite end thereof, as the volume of the sound, directed into themicrophone, increases or decreases. That is, as the volume of the soundincreases, the incandescent lamps are lighted progressively, whereuponanyone within visual range of the device is informed as to the volume ofthe sound.

Preferably, the device is constructed in the form of a cabinet it. Themicrophone ll may be attached in, or to, the cabinet, or located at anysuitable place, or the microphone of a public address system, or thelike. may be used. The series of incandescent lamps l2 to 23 arearranged preferably in a vertically extending row in the front wall ofthe cabinet. A lead 25 is provided for connecting the device to anordinary convenience outlet. With this arrangement, the device iscompact and self-contained, and the only connection necessary to be madeis to the power supply by plugging in the lead 25.

As previously stated, the device includes mechanism for progressivelyconnecting the incandescent lamps l2-23 to the power supply. That is,each lamp is energized by a sound intensity, one or more decibels higherthan the one below it. As illustrated in the drawings, this is broughtabout by the use of a thyratron tube 21 associated with each of theincandescent lamps. The common side of the lead 25 is connected to-afuse 28, and the hot side to a main operating switch 29; This switch isconnected to a wire 30 which, in turn, is connected to one side of allthe incandescent lamps through wire 3|. The opposite side of each of thelamps is connected to the plate 33 of the respective tubes 21. Thecathodes 34 of the tubes 21 are connected to the wire'35, and to thefuse 28 through wires 36, 31.

The thyratron tubes 21 act in the nature of switches to connect anddisconnect the lamps I2 to 23, respectively, to the power supply. Thetubes are caused to so function by amplifying the output signal of themicrophone it through a three stage amplifier including the amplifyingtubes 38, 39 and 40. The output of the final stage is rectified by thetube M, one side of this tube being connected to a wire 82, through wireit, and the opposite side of the tube is connected to a. wire 4t,through wire 45. A series of voltage dividers 46 are connected acrossthe wires 42, (it, and the movable contacts 48 thereof are connectedrespectively to the grids 49 of the tubes H.

The voltage divider 46, connected to the grid of tube 21 controlling theincandescent lamp positioned at one end of the-series of lamps, such asthe lamp l2 at the bottom of the row, is adjusted so that the fullvoltage, or nearly full voltage.

impressed upon the wires 42, 44, is applied to the grid of that tube 21,and the movable contacts of the other dividers are adjusted so that thevoltage applied to the grids 49 of the tubes 21 is progressively reducedso that the grid voltage of the thyratron controlling the top lamp 23 isthe least.

50 lighted progressively from the bottom to the top.

The device is provided with a power supply transformer 50 having taps 5ito supply current to the heaters of the amplifying tubes 38, 39, 40, andrectifying tube 4|, a winding 52 to supply 55 filament current to arectifier 53. and a winding 3 it for one side it of the D. C. amplifiersupply A transformer to is also provided toenergiae the heaters of thetubes 21 by the secondary leads 6 I.

The circuit and arrangement of the amplifying unit, including the tubes38, 38, 40, is of conventional design and it is not believed necessaryto explain that portion of the circuit in detail. Attention is called tothe variable gaincontrol -63 connected in the plate circuit of theamplifying tube 38.

The function of the variable gain control 83 is to initially adjust thedevice for proper operation in any particular situation. For example, ifthe device is being used to inform a speaker as to the volume of hisvoice in a small room, the gain control 63 is adjusted so that theseries of lamps 12-23 will properly indicate the range of volume forthat situation. That is, the gain control would be adjusted to reducethe current supplied to the second amplifying tube 39. If the device, onthe other hand, is being so used in a large hall, or auditorium, wherethe microphone is located a greater distance from the speaker, the gaincontrol is adjusted to increase the current to the second stage ofamplification and accordingly, that which is impressed upon the line42-44. There are also instances where it is desirable to initiallyadjust the gain control to make the device less sensitive, in order toeliminate the influence of outside sounds, such as street noises, etc.

The voltage dividers 46 are adjusted so that each of the lamps 12-23will be illuminated progressively by an increase in sound volume, orintensity, of one or more decibels higher than the one below it. I havefound that when the device is used as a volume indicator for speech, thesetting of the voltage dividers in steps of two decibels issatisfactory. Accordingly, when sound of a given volume is directed intothe microphone II, and the gain control 63 is properly adjusted, thelowermost lamp l2 will be energized through the tube 21 which is trippedby the positive voltage produced by the rectifier tube H, as previouslyexplained. Each increase of two'decibels in the volume of the sound, thetubes 21 will be successively and progressively tripped and accordingly,the lamps 12-24 will likewise be progressively energized and with asound of given volume, all of the lamps will be simultaneously energizedup to and including the lamp controlled by the tube 21 tripped by thevoltage impressed thereon by that sound signal, and it will be apparentthat if the volume of sound is decreased, the indicating lamps will beprogressively deenergized, whereby the lamps are progressively energizedand deenergized directly in proportion to the rise and fall of thevolume of the sound directed into the microphone.

It will be observed that since the tubes 21 have alternating currentsupply in their plate circuits, they are automatically and substantiallyinstantaneously restored to a non-conducting condition when the gridexcitation is removed. When the device is used to indicate sound volumewhich fluctuates rapidly, such as speech, the duration of the peak ofthe sound intensity is rather short for proper visual indication. Thisduration may be varied by selecting one of a plurality of condensers,such as It, H, II, shunted across the output of the rectifying tube 4|.These condensers are of different capacity, and the greater thecapacity, the greater the damping effect. The condensers are selectivelyconnected in a circuit by a movable contact 13 which is operated by aknob Ii arranged on the face of the cabinet It.

A dial 16 is provided to indicate the condenser selected. Preferably,the condenser of greatest capacity has a capacity which will provide atime factor of about one and one-half seconds. With this time lag, thedevice disregards peaks entirely and reads mean values. The condenser ofleast capacity is such as to provide a substantially instantaneousindication, and the intermediate condenser, or condensers havingcapacity somewhere between the end condensers of high and low capacity.

The variable contact of the adjustable gain control 63 is operated by aknob 11 also available on the face of the cabinet, and a dial I8 isprovided to indicate the setting of the contact. Preferably, the dial itis graduated so that the movable contact of the gain control can beadjusted in steps equivalent to two decibels each. It has been foundthat this arrangement gives an effective adjustment for the device whenit is used for a voice volume indicator. However, it is apparent thatadjustments of any magnitude can be effected for any particular use towhich the device may be put.

Sufiicient bias is taken from the amplifier power supply 55, 56, andapplied to the grids of the tubes 21 to make certain that the tubes willbe normally non-conducting. A load resistor is provided with a movablecontact 8| connected to the ground support 36. By adjusting the movablecontact 8!, the negative bias to the tubes 21 can be adjusted so thatthe tubes cut oil sharply when no current is supplied to the grids ofthe tubes from the circuit 42, 44. This adjustment is in the nature ofan initial adjustment made when the tubes 21 are installed, or when anyone or more of the tubes are replaced, as will be well understood bythose familiar with the art.

What I claim is:

A decibeloscope for visually indicating sound volum comprising aplurality of electric lamps arranged in a vertical row, a power supplyfor energizing said lamps, a microphone, inertia free means connected incircuit with said microphone and operable to progressively connect saidlamps to said power supply in proportion to the volume of the sounddirected into said microphone, and means adjustable to control theduration said respective lamps are connected to the power supply afterthe sound volume has decreased.

RUDOLPH W. STANMYRE.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,120,971 Bailey June 21, 19382,179,101 Read, Jr Nov. 7, 1939 2,331,236 Schaefer Oct. 5, 19432,398,046 Schaefer Apr. 9, 1946 2,407,286 Kinkead Sept. 10, 1946

